Various optically switchable devices are available for controlling tinting, reflectivity, etc. of window panes. Electrochromic devices are one example of optically switchable devices generally. Electrochromism is a phenomenon in which a material exhibits a reversible electrochemically-mediated change in an optical property when placed in a different electronic state, typically by being subjected to a voltage change. The optical property being manipulated is typically one or more of color, transmittance, absorbance, and reflectance. One well known electrochromic material is tungsten oxide (WO3). Tungsten oxide is a cathodic electrochromic material in which a coloration transition, transparent to blue, occurs by electrochemical reduction.
Electrochromic materials may be incorporated into, for example, windows for home, commercial, and other uses. The color, transmittance, absorbance, and/or reflectance of such windows may be changed by inducing a change in the electrochromic material, that is, electrochromic windows are windows that can be darkened or lightened electronically. A small voltage applied to an electrochromic device of the window will cause it to darken; reversing the voltage causes it to lighten. This capability allows for control of the amount of light that passes through the window, and presents an enormous opportunity for electrochromic windows to be used not only for aesthetic purposes but also for energy-savings. With energy conservation being of foremost concern in modern energy policy, it is expected that growth of the electrochromic window industry will be robust in the coming years.
An important aspect of electrochromic window fabrication is coating of material layers (e.g., thin films) on a substantially transparent substrate (e.g. glass) to form an electrochromic device stack. Part of fabrication includes removing portions of the EC device stack to make it functional and/or masking to pattern the device. For example, laser patterning of various layers are employed to make EC devices functional, e.g. to configure electrical connectivity and other aspects of the device's configuration on a substrate.